U.S. General David Petraeus (right) talks with U.S. Democratic presidential candidate Barack Obama as they fly over Baghdad.

Senator Barack Obama, the presumed U.S. Democratic candidate for president, is wrapping up a two-day stop in Iraq which has seen him meet Iraqi government leaders, former Sunni insurgent leaders, and U.S. military commanders.

The tour has not only been to listen but also, whenever possible, reach conclusions with his interlocutors that clearly distinguish him from his Republican rival, Senator John McCain.

And in Iraq on July 21, he found the issue: a time frame for U.S. troop withdrawals.

Coming out of a meeting with Iraqi Prime Minister Nuri al-Maliki, Obama initially only said his meeting was informative and useful, saying, "We had a very constructive discussion."

But shortly afterward, he announced that al-Maliki had expressed support for a pullout of U.S. troops from Iraq by 2010. That would be very close to Obama’s own promise to U.S. voters to withdraw U.S. combat forces from Iraq within 16 months after taking office in January.

Stopped Short Of Endorsement

Al-Maliki's spokesman confirmed after the meeting that the prime minister hoped U.S. combat troops will withdraw in 2010, but stopped short of endorsing Obama's 16-month pledge.

The discussion of a time frame -- which is currently also part of negotiations between Washington and Baghdad over the future status of U.S. troops in Iraq -- immediately became the day's "hot button" in the Obama-McCain debate.

McCain, who was on a visit to former President George H.W. Bush in Kennebunkport, Maine, dismissed the talk of time frames by saying that "when you win wars, troops come home." He argues that a longer-term U.S. presence is needed to preserve security gains.

The two candidates also exchanged sharp words over whether Obama was wrong to oppose the U.S. troop surge, which began in 2007 and is widely credited with helping to reduce violence in Iraq.

McCain, who strongly supported the surge, said on July 21 that he hoped his rival would "admit he badly misjudged the situation."

But Obama, while praising the surge on July 21, said that it worked because it was matched by events no one had anticipated -- the turning of former Sunni insurgents against Al-Qaeda and a reduction of Shi'ite militia violence.

"Had those political factors not occurred, I think that my assessment would have been correct," Obama told the U.S. television network ABC.

Importance Of Appearances

The campaign debate, uninterrupted no matter where Obama and McCain are at the moment, underlines how much importance both camps now place on their candidates assuming the role of world leaders in the run-up to the November election

Obama is determined to shake off McCain’s charges that he is less experienced in foreign policy, and the success of his trip will be measured by how much rapport he can demonstrate with the heads of government and state he meets.

He will have many more opportunities -- and tests -- as his world trip continues through July 26.

From Iraq, he travels on July 22 to Jordan and then on to Israel and the Palestinian territories.

In Israel and the Palestinian territories, he will meet with both Israeli leaders and -- importantly -- with Palestinian Authority President Mahmud Abbas. The Abbas meeting will distinguish Obama again clearly from McCain, who visited Israel in March but did not travel to the West Bank.

The Israel visit is also likely to highlight differences between Obama and McCain over whether Washington should negotiate with Tehran over Iran's nuclear program. Obama's openness to talking to Iran has been criticized by many Israelis who view Iran as an immediate regional threat.

McCain, speaking to an Israeli TV station in advance of Obama’s arrival, said he favors stiffer sanction to stop Iran’s threats against Israel. He added, "The United States of America can never allow a second Holocaust."

From the Mideast, Obama travels on to Europe, where he is expected to visit Berlin on July 24, Paris on July 25, and London on July 26.